Inspection of objects such as wafers or reticles using a scanning electron beam inspection tool is known in the art. Single beam inspection tools scan a wafer or reticle by a single beam. The relative size difference between wafers size and the beam cross section the throughput of such systems is limited.
In order to increase the throughput of inspection and metrology systems various techniques were suggested. A first technique include scanning only a portion of the wafer or reticle. This portion usually include multiple regions of interest that are positioned in various locations.
Another technique involves using multiple beam scanning arrays. Some multiple-beam systems include fixed arrays of beams, starting from line arrays to two dimensional grid arrays.
The following U.S. patents and U.S. patent applications, all being incorporated herein in reference, provide a brief overview of some state of the art multiple beam scanning systems: U.S. Pat. No. 6,465,783 of Nakasuji entitled “High-throughput specimen-inspection apparatus and methods utilizing multiple parallel charged particle beams and an array of multiple secondary-electron-detectors”; U.S. Pat. No. 6,734,428 of Parker et al. entitled “Multi-beam multi-column electron beam inspection system”; U.S. Pat. No. 6,750,455 of Lo et al. entitled “Methods and Apparatus for Multiple Charged Particle Beams”; U.S. Pat. No. 6,803,572 of Veneklasen, et al. entitled “Apparatus and methods for secondary electron emission microscope with dual beam”; and U.S. patent application publication No. 2002/0015143 of Yin et al. entitled “Multi-Beam Multi-Column Electron Beam Inspection System”.
There is a need to provide an efficient system and method for scanning an object, using a multiple beam array.